targeted-toxins

Miller SA, Lappi DA, Wiley RG (2000) Intrathecal dermorphin-saporin decreases morphine effect in hotplate algesia testing. Neuroscience 2000 Abstracts 212.8. Society for Neuroscience, New Orleans, LA.

Summary: The targeted cytotoxin, dermorphin-saporin, selectively destroys cells expressing MOR. In the present study, we gave dermorphin-saporin by lumbar i.t. injection and sought to determine if destroying dorsal horn neurons expressing MOR would alter thermal sensitivity and/or response to systemic morphine (MS) using hotplate testing under various conditions. 16 male Sprague-Dawley rats were tested on constant temperature (0.3, 44 and 47 C) and incremental (0.1 C/sec from 28 to 57 C) hotplates. Then 8 rats received lumbar intrathecal injections of derm-sap (465 ng) and 8 received vehicle using a subarachnoid PE-10 catheter that was removed 10 mins after injection. Retesting rats after toxin/vehicle injection showed no change in responses to any of the hotplate conditions. However, vehicle but not derm-sap rats showed increased lick latency on the incremental hotplate 20 mins after MS, 2.5 mg/kg, s.c. At 5 mg/kg of MS, vehicle and dermorphin-saporin rats showed identical responses. Capsaicin cream (0.94%) applied to the plantar surface of both hindpaws 3 hrs before testing on the 44 C hotplate produced decreased lick latencies in both groups of rats. MS, 5 mg/kg, s.c., produced increased lick latencies in capsaicin treated vehicle but not derm-sap rats. At 10 mg/kg, MS produced identical effects in capsaicin treated vehicle and toxin rats. These results indicate that i.t. derm-sap produced no change in baseline thermal sensitivity but did diminish the effect of low dose MS under conditions that preferentially test C nociceptor function suggesting that MOR-expressing dorsal horn neurons play a role in the analgesic action of low dose MS.

Related Products: Dermorphin-SAP / MOR-SAP (Cat. #IT-12)

Vierck CJ, Belford PM, Iqbal MA, Camara C, Kline RH, Lappi DA, Wiley RG (2000) Altered operant and reflex responses to noxious heat in rats with central noradrenergic lesions using antiDßH-saporin. Neuroscience 2000 Abstracts 247.10. Society for Neuroscience, New Orleans, LA.

Summary: We sought to determine effects of a selective lesion of pontine NA neurons on thermal sensitivity, using an operant escape task and hotplate tests. 8 rats received ICV injections of 10 ìg of anti-DβH-saporin, an immunotoxin that selectively destroys NA neurons, or vehicle. The rats were trained to escape a dark chamber with a hot floor to a brightly lit room-temperature shelf. There was no difference between groups at 39o, 44oor 47o C. However, at 44o C, application of mustard oil to the dorsal surface of both hindpaws or 0.94% capsaicin cream to the plantar surfaces increased escape durations only for vehicle rats. Also, at 44o C, toxin-treated rats were more sensitive than vehicle rats to morphine (0.5-5 mg/kg, s.c.) and clonidine (0.125 mg/kg, s.c.). The toxin-injected rats were insensitive to yohimbine (2.5 and 5 mg/kg, s.c.). Postmortem analysis for DβH showed that toxin-treated rats lost all pontine NA neurons, with preservation of medullary NA cells. To determine the role of NA projections to the spinal cord, two groups of rats were injected with 200-300 ng of antiDβH-saporin or vehicle via a lumbar intrathecal catheter. There were no consistent changes in baseline responses, and no differences between toxin and vehicle injected rats to 44o C after capsaicin or morphine (2.5 mg/kg, s.c.). However, the toxin treated rats were more sensitive to clonidine (0.03 mg/kg, s.c.). Thus, spinally projecting NA neurons appear not to mediate some modulatory effects of pontine NA neurons on nociception.

Related Products: Anti-DBH-SAP (Cat. #IT-03)

Easton A, Ridley RM, Baker HF, Gaffan D (2000) Crossed unilateral lesions of the cholinergic basal forebrain (by me20.4IgG-saporin) and fornix from inferior temporal cortex produce severe learning impairments in rhesus monkeys. Neuroscience 2000 Abstracts 205.8. Society for Neuroscience, New Orleans, LA.

Summary: Section of the anterior temporal stem, amygdala and fornix in monkeys results in a dense anterograde amnesia. We have proposed that this impairment is a result of isolating the medial temporal lobe and inferior temporal cortex from their basal forebrain afferents. Evidence suggests that the cholinergic cells of the basal forebrain are important for learning and memory. In the present experiment we have made an immunotoxic unilateral lesion (ME20.4IgG-saporin), specific for the cholinergic cells of the basal forebrain, in combination with unilateral fornix damage in the same hemisphere, and a lesion of the inferior temporal cortex in the opposite hemisphere to disconnect these cholinergic cells from the medial temporal lobe and inferior temporal cortex. These monkeys were severely impaired at scene learning and concurrent visual discrimination learning, both of which are sensitive to sections of the anterior temporal stem, amygdala and fornix. This deficit is strongly correlated with the degree of acetylcholine loss in the basal forebrain in the hemisphere with the immunotoxic lesion. This result strengthens the proposal that the cholinergic cells of the basal forebrain are essential for new learning, and that their interaction with the medial temporal lobe and inferior temporal cortex is required for normal learning in monkey and man.

Related Products: ME20.4-SAP (Cat. #IT-15)

McGaughy J, Everitt BJ, Robbins TW, Sarter M (2000) The role of cortical cholinergic afferent projections in cognition: impact of new selective immunotoxins. Behav Brain Res 115:251-263. doi: 10.1016/s0166-4328(00)00262-x PMID: 11000424

Summary: Discusses the advancements of animal models through immunotoxins targeting cholinergic neurons, 192-IgG-SAP (IT-01) and ME20.4-SAP (IT-15), and how their selectivity has allowed Alzheimer’s research advancements. Discusses the benefits of immunotoxin animal model studies over neuropsychological, psychopharmacological and excitotoxic studies.

Related Products: 192-IgG-SAP (Cat. #IT-01), ME20.4-SAP (Cat. #IT-15)

Bitner RS, Nikkel AL, Decker MW (2000) Immunohistochemical detection of alpha-7 nicotinic receptor expression by two distinct cell types in the dorsal raphe and locus coeruleus of rat. Neuroscience 2000 Abstracts 41.7. Society for Neuroscience, New Orleans, LA.

Summary: The α7 nicotinic acetylcholine receptor (nAChR) subunit can be assembled to form a homomeric-pentamer with high permeability to calcium, in contrast to other neuronal nAChR subunit-comprised ligand-gated cation channels. Although the expression of the α7-nAChR has been demonstrated throughout the CNS, the neurochemical phenotype of neurons expressing α7 remains to a large extent unknown. Using a polyclonal antibody raised against the carboxyl terminus (amino acids 460-479) of the α7 nAChR subunit (goat IgG, Santa Cruz Biotech.), immunohistochemical staining was observed in rat dorsal raphe (DR) and locus coeruleus (LC), serotonergic and noradrenergic brainstem nuclei, respectively. In both the DR and LC, there appeared to be two histologically distinct α7-expressing cell types as distinguished by size, i.e. large vs. small diameter. In rats treated with either a selective serotonergic (5,7-dihydroxytryptamine 150 μg i.c.v.) or noradrenergic (anti-dopamine-β-hydroxylase saporin 5 μg i.c.v.) neurotoxin, α7 immunostaining was seen only in small diameter cells, suggesting that the large diameter α7-expressing cells were serotonergic DR and noradrenergic LC neurons. Indeed, double-labeling experiments revealed in the large, but not small, cell types coexpression of α7 with tryptophan hydroxylase in the DR and tyrosine hydroxylase in the LC of saline-treated rats. In contrast, there was no coexpression in the neurotoxin-treated rats due to the loss of serotonergic or noradrenergic neurons, with only small diameter α7-expressing cells remaining. The results of these studies suggest that both serotonergic and noradrenegic neurons express α7 nAChRs. In addition, there appears to be a small diameter, non-serotonergic/noradrenergic cell-type in both the DR and LC that also expresses α7.

Related Products: Anti-DBH-SAP (Cat. #IT-03)

Rahimi O, Tatham D, Juliano SL (2000) Sensory training improves the ability to process stimuli in barrel cortex after basal forebrain lesion. Neuroscience 2000 Abstracts 51.22. Society for Neuroscience, New Orleans, LA.

Summary: Lesions of the basal forebrain deplete the cerebral cortex of acetylcholine and result in decreased ability to process stimuli. Using a model of unilateral basal forebrain lesion (BFL), we previously determined that the ability to perceive simple touch to the whiskers is impaired after BFL, but improves over time. Functional responses in barrel cortex, however, as measured by 2-deoxyglucose uptake (2DG) or electrophysiological recordings, remain reduced even after long survival times. We questioned whether the impaired cortical responses could be improved with behavioral training involving sensory discrimination using the whiskers. To do this, one group of rats was trained to discriminate between different textures using the whiskers on one side of the face, which projected to the lesioned hemisphere. After learning the task, this group of rats received a BFL using the immunotoxin, 192-IgG Saporin. They then continued the sensory discrimination task for at least 2 months. The second group of rats received a BFL, but no sensory training. They survived after the lesion for comparable periods of time; each rat of both groups then underwent a 2DG experiment. During the 2DG study, 1-4 matched sets of whiskers on both sides of the face were stimulated using an electromagnetic device. The magnitude of the response was measured in barrel cortex by preparing 2-dimensional maps of the label evoked by whisker stimulation. The area of barrel cortex activated in each hemisphere by whisker stimulation was measured and expressed as a ratio of the lesioned to normal hemisphere. We found that the evoked response in the lesioned hemisphere remained diminished compared to the normal side regardless of training. When the magnitude of response was compared between the trained and untrained group, however, the area of 2DG uptake in each barrel in response to stimulation was significantly increased in the animals receiving sensory discrimination training. These findings suggest that sensory training plays a role in improving cortical responses to stimulation after lesion of the basal forebrain.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Daniels D, Miselis RR, Flanagan-Cato LM (2000) Local immunotoxin treatment prevents transneuronal labeling of the intermediolateral column; but not the ventral horn; of the spinal cord after tracer injection into lumbar epaxial muscle. Neuroscience 2000 Abstracts 77.13. Society for Neuroscience, New Orleans, LA.

Summary: Pseudorabies virus (PRV) has been used as a transneuronal tracer to study central neural circuits that control various peripheral targets. Our laboratory has injected PRV into the lumbar epaxial muscles that produce the lordosis posture to label sequentially specific brain regions along the neuraxis. However, concomitant uptake of PRV through sympathetic innervation of nearby vasculature has made the interpretation of higher-order labeling problematic. To avoid this confound, we have designed a procedure for focal sympathetic denervation using dopamine-β-hydroxylase immunotoxin (DHIT). Five days after injecting DHIT (5 μg) into the medial portion of lateral longissimus, the Bartha strain of PRV was injected into the pre-treated area. After survival times of 72 or 96 h, animals were sacrificed and the spinal cords were immunostained for PRV. In preliminary studies, DHIT treatment was not effective in all animals, as determined by PRV labeling in the sympathetic preganglionic neurons that reside in IML. However, at each survival time, in 50% of the animals DHIT virtually eliminated PRV-labeling in cells within IML of the thoracic and lumbar spinal cord, whereas robust labeling of motoneurons in the ventral horn was retained. These preliminary results suggest that this procedure for local sympathectomy may allow for selective transneuronal labeling of somatic motor pathways.

Related Products: Anti-DBH-SAP (Cat. #IT-03)

Grindstaff RJ, Grindstaff RR, Cunningham JT (2000) Baroreceptor sensitivity of rat supraoptic vasopressin neurons involves noncholinergic neurons in the DBB. Am J Physiol Reul Integr Comp Physiol 279:R1934-R1943. doi: 10.1152/ajpregu.2000.279.5.R1934

Summary: Baroreceptors are one component of the system that buffers acute changes in blood pressure. Part of this control stems from the baroreceptor ability to regulate vasopressin release from the neurohypophysis. Using 192-Saporin (Cat. #IT-01) to specifically eliminate cholinergic neurons in the diagonal band of Broca, Grindstaff et al. demonstrated that these neurons are not utilized in the pathway that relays baroreceptor information to the brain.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Schreihofer AM, Guyenet PG (2000) Role of presympathetic C1 neurons in the sympatholytic and hypotensive effects of clonidine in rats. Am J Physiol Regul Integr Comp Physiol 279:R1753-R1762. doi: 10.1152/ajpregu.2000.279.5.R1753

Related Products: Anti-DBH-SAP (Cat. #IT-03)

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Schreihofer AM, Stornetta RL, Guyenet PG (2000) Regulation of sympathetic tone and arterial pressure by rostral ventrolateral medulla after depletion of C1 cells in rat. J Physiol 529(1):221-236. doi: 10.1111/j.1469-7793.2000.00221.x

Summary: The rostral ventrolateral medulla (RVLM) controls and maintains basal sympathetic vasomotor tone, and is also vital to many sympathetic reflexes. Sympathetic nerve activity and arterial pressure correlate with the C1 adrenergic neurons in the RVLM, but there are also non-catecholaminergic neurons present. Schreihofer et al. used anti-DBH-SAP (Cat. #IT-03) to eliminate the C1 cells of the RVLM to investigate the non-catecholaminergic neuron contribution to vasomotor tone. Their data indicate C1 cells are necessary for full expression of sympathoexitatory responses generated by the RVLM.

Related Products: Anti-DBH-SAP (Cat. #IT-03)

Read the featured article in Targeting Trends.